Windows Startup & Blue Screen Codes: What They Mean + Safe Recovery Steps

Use this guide to identify whether you have a boot-path failure, update/installer failure, or driver/permissions issue, then apply safe recovery steps before risky changes.

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TL;DR

✓ Start with where the code appears: boot screen vs update/install vs app.
✓ Boot failures often relate to boot order, disk detection, or bootloader configuration.
✓ Update failures often relate to prerequisites, component store state, or permissions.
✓ If disk read errors appear, prioritize data recovery.

Quick Navigation

Symptoms Root Causes Step-by-step fixes What NOT to do If it persists Code directory Related guides & hubs FAQ References

Symptoms / When you see this

✓ Bootloader messages like “BOOTMGR is missing”.
✓ Hex codes during updates/installs.
✓ Upgrade fails and rolls back.

Root causes (grouped)

✓ Boot order and UEFI/Legacy mismatch.
✓ Disk read issues or unstable storage.
✓ Update servicing/prerequisite failures.
✓ Connectivity/timeouts during updates.
✓ Driver compatibility issues during feature upgrades.

Step-by-step fixes (safe, prioritized)

✓ Remove external USB media and confirm correct boot device.
✓ Confirm boot mode matches installation (UEFI vs Legacy).
✓ Ensure stable internet and sufficient storage for updates.
✓ Use official recovery tools for boot repair if needed.
✓ Avoid destructive resets until you have a backup path.

What NOT to do

✓ Do not repeatedly force power off; it can worsen corruption.
✓ Do not change partitions without backups.
✓ Do not trust random “fix” tools; use official recovery workflows.

If it persists (escalation checklist)

✓ Capture exact code and screen context.
✓ Check whether drive is detected and has health warnings.
✓ Use setup/servicing logs for update failures.
✓ Seek help when data recovery is required.

Code directory within this guide

✓ Stop codes vary by Windows version and drivers. When you don’t see your exact stop code, use logs to identify the failing layer.

Code	Meaning	Next step
0x8007045D	I/O device error — Windows reported an input/output error while reading from or writing to a device.	Follow the checklist on the code page
0x80070570	File is corrupted — A required file could not be read because it is corrupted or inconsistent.	Follow the checklist on the code page
0x800705B4	Operation timed out — A Windows operation exceeded its allowed time limit and timed out.	Retry once; validate connectivity and service status
0x80070643	Installation failed — A Windows installer or update component reported a fatal error and could not complete the install.	Confirm storage/prerequisites; retry after restart
0x80072EE2	Connection timed out — A Windows network request timed out before it could complete.	Retry once; validate connectivity and service status
0x80072EFD	Cannot connect — Windows could not establish a connection to the required service endpoint.	Check network path, firewall/proxy, and service availability
0x800F0922	Update failed — A Windows update or feature installation could not complete due to a servicing or connectivity requirement.	Confirm storage/prerequisites; retry after restart
0x80240017	Update not applicable — Windows Update determined an update or component does not apply to the current system state.	Confirm storage/prerequisites; retry after restart
0xC1900101	Rollback due to driver issue — A Windows upgrade failed and rolled back, commonly when a driver causes a compatibility or stability problem.	Follow the checklist on the code page
0xC1900223	Feature update error — A Windows feature update failed due to a prerequisite, compatibility, or download/servicing issue.	Confirm storage/prerequisites; retry after restart
0x80004005	Unspecified error — A generic failure occurred and the system did not expose a specific reason.	Follow the checklist on the code page
0x80070002	File not found — A required file could not be located at the expected path.	Verify the correct path/resource and prerequisites
0x80070003	Path not found — A required directory or path was missing or not reachable.	Verify the correct path/resource and prerequisites
0x80070005	Access denied — An OS access control check blocked the requested operation.	Verify account permissions and security policy
0x80070057	Parameter incorrect — An operation failed because an input value was invalid for the requested action.	Follow the checklist on the code page
0x80070490	Element not found — A required component or referenced item was not found in the expected state.	Verify the correct path/resource and prerequisites
A DISK READ ERROR OCCURRED	Disk read failure — The system failed to read from the boot disk during early boot.	Follow the checklist on the code page
BOOT FAILURE	Insert system disk — Firmware could not boot from the current device and is prompting for bootable media.	Follow the checklist on the code page
BOOTMGR IS MISSING	Boot loader missing — The system cannot find the Windows Boot Manager on the selected boot device.	Verify the correct path/resource and prerequisites
DISK BOOT FAILURE	Boot device not bootable — The selected disk does not contain a valid boot record for the current boot mode.	Follow the checklist on the code page
INVALID PARTITION TABLE	Boot partition issue — The system found an invalid or non-bootable partition table on the selected drive.	Follow the checklist on the code page
NTLDR IS MISSING	Legacy boot loader missing — The system is attempting a legacy boot but cannot find the required loader on the boot device.	Verify the correct path/resource and prerequisites
OPERATING SYSTEM NOT FOUND	No OS detected — Firmware could not find a bootable operating system on the selected device.	Verify the correct path/resource and prerequisites
PRESS ANY KEY TO BOOT	Booting from external media — The system detected bootable external media and is asking whether to boot from it.	Follow the checklist on the code page
PXE BOOT FAILED	Network boot fallback — The system attempted to boot from the network (PXE) and failed, often after it couldn’t boot from local storage.	Follow the checklist on the code page
REBOOT AND SELECT PROPER BOOT DEVICE	Wrong boot device — Firmware cannot find a bootable device from the current boot order selection.	Follow the checklist on the code page
BOOT DEVICE NOT FOUND	Boot device unavailable — Firmware could not locate the configured boot device or boot partition.	Verify the correct path/resource and prerequisites
CMOS BATTERY FAILURE	RTC/CMOS battery issue — Firmware reported that the battery maintaining time/settings is not functioning correctly.	Follow the checklist on the code page
CMOS CHECKSUM BAD	Firmware settings invalid — Firmware reported that stored configuration data failed validation.	Follow the checklist on the code page
CPU FAN ERROR	Cooling issue detected — Firmware detected a problem with CPU cooling fan operation.	Follow the checklist on the code page

Tip: If your exact code isn’t listed, use the closest hub link above and browse related prefixes or message patterns.

FAQ

Are boot messages the same as Windows errors?

No. Boot messages come from firmware/bootloader stages before Windows fully loads.

Safest first check?

Confirm boot order and remove external boot media that might take priority.

Why do updates fail with generic codes?

Many codes are category-level signals; logs are needed for the underlying cause.

When should I back up?

When disk read errors appear or boot loops repeat. Data recovery becomes priority.

Is factory reset always needed?

No. Many issues can be resolved via boot repair, update repair, or driver fixes.

Can driver cause rollback?

Yes. Feature upgrades can roll back due to incompatible drivers or conflicts.

Does UEFI/Legacy mode matter?

Yes. Mismatch can prevent boot.

What logs matter?

Setup/servicing logs and installer logs where applicable.

References / Notes

✓ Official Windows recovery documentation
✓ Device OEM support guidance
✓ Servicing and setup log references